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Pigeon Infestation & Health Hazards in Buildings

Oct 28, 2014





Feral pigeons (Columbia livia var. domestica) can be a nuisance and may cause significant damage to buildings.  If feral pigeons take up residence within a disused property they can seriously damage the interior historic fabric, contents and finishes.  It is vital to take measures to minimise pigeon activity in and around buildings in order to avoid additional maintenance issues and significant problems for renovation projects.  

Rectifying the damage caused to the fabric of a property by pigeon guano (bird excreta) is expensive and in most cases avoidable.  There are many methods of pigeon control including bird proofing, wire deterrent systems, netting, bird spikes and a large variety of electrical and sonic bird deterrent solutions.



Feral pigeons and other birds make nests regularly and roost outside and inside our buildings.  Architects, surveyors, construction professionals and maintenance staff are all familiar with the damage that can be caused by these birds sharing our environment.



Feral pigeons are believed to have descended from rock doves that interbred with racing pigeons and pigeons from domestic pigeon lofts.  Skyscrapers and similar tall buildings provide ideal habitats, very similar to the cliff homes of their pigeon ancestors.

These pigeons have thrived by adapting to life in and around our buildings and have learnt to roost and breed very successfully within this environment.  They thrive on a plentiful supply of our dropped and dumped food scraps.  As they have adapted so excellently to this style of living, they have sometimes been called "the flying rat".  It’s no surprise that over recent years there has been a marked increase in the numbers of feral pigeons.


Adult Pigeons

The adult pigeon is about 33cm in length and weighs between 280 and 560g, an average of about 350g.  Its plumage can vary considerably, from a close resemblance to that of the original rock dove (with blue-grey plumage, double black wing bars and a white rump), through to various blues, reds, chequered and almost black types.  Colours vary considerably from blue-grey, through blues, reds, mottled patterns and charcoal to almost pure white (Simms, 1979).  

The birds will roost and nest on horizontal building surfaces and any other structures that provide a small amount of shelter from the elements.  Balconies, flat roofs, ledges, loft spaces and empty buildings are often used if the birds have access.  

Nests are constructed of twigs but can also contain pieces of plastic and other debris.  They may even be built on or near the dead bodies of other pigeons. Their natural food is grain and green vegetable matter but they will scavenge food and eat almost any foodstuff available such as dropped takeaway foods.


Life Cycle

The Feral Pigeon is capable of breeding throughout the year and nests may be found in any month.  However the peak occurs between March and July.  Usually, two white eggs are laid on consecutive days and incubation is shared between both adults.  Incubation lasts for about 18 days, with fledging taking place about 4 ½ weeks later.  A new clutch can be laid when the first young are just 20 days old.  Therefore up to nine broods may be produced per year by just one female pigeon and pigeons may live as long as thirty years (P Ehrlich et al, 1988)


Deterioration and Damage to Buildings

Pigeon droppings are not only unsightly; their acid content can lead to the deterioration of soft stone and cause long-term damage to buildings (Bassi and Chiantante, 1976; Howard and Oldsbury 1991).  The accumulation of pigeon droppings can deface the finishes of the exterior facade and the interior of the building.  Removal is not only difficult and expensive but can cause more damage than the droppings in the first place (D Channon, 2004).

Nest droppings and feathers block gutters and rainwater pipes causing water damage to buildings.  Their droppings can lead to hazards on pavements, especially for the elderly.  Pigeons are capable of lifting loose roof coverings, tiles and battens to gain entry into the roof voids.  This can significantly damage the structure by allowing water penetration, providing the ideal environmental conditions for the growth and proliferation of wood rotting fungi.  Wood boring insects are attracted to this damp, rotting environment, leading to substantial further decay (Singh 1995).  

Pigeon nesting materials, feathers and faeces can block parapet gutters and hopper heads, allowing water penetration into the building fabric and providing the ideal environmental conditions for the growth and development of decay organisms (Singh 1994a, & Singh 1999).

In poorly maintained and unoccupied buildings, where significant undetected water ingress has occurred, major outbreaks of dry rot (Serpula lacrymans) and wet rots establish and thrive.  These include (Coniophora puteana, Antrodia xantha, A. searilis, A. vaillantti & Phellinus contiguus).  Thesubsequent deterioration to the historic fabric, finishes and contents is an inevitable consequence (Singh 1994).  Sometimes this deterioration is so dramatic that many of the important historical and architectural features are destroyed beyond repair.

Early-morning activity around nesting areas can cause a public nuisance, as can pestering for food. Around public and buildings of historic and touristic interest further problems can arise as the visitors start feeding pigeons.   Their numbers will increase dramatically, leading to extensive faeces and fouling.

Ladders and fire escapes coated in pigeon droppings become slippery and unsafe to use particularly in wet conditions.  Startled pigeons may take flight suddenly and cause a hazard to road traffic.



Pigeons and the Law

  • Most birds, their nests and eggs are protected under the Wildlife and Countryside Act 1981.
  • The act allows the control of certain birds, including feral pigeons, by authorised people using specified methods.
  • The use of spring traps, poisons, certain types of nets, gassing and sticky substances that may entangle a bird is illegal.


Health Hazards

Large populations of pigeons and other birds inhabiting buildings or living on the facade for many years may present a potential risk of disease to people in and around these buildings (Weber, 1979).

The organic, nutrient rich accumulation of pigeon droppings, including feathers, detritus and debris under a nest provides an ideal environment for disease.  This encourages fungi and bacteria to grow and proliferate.  External parasites may also become a problem when infested pigeons or bats leave their roosts or nests. These parasites can infest buildings and cause health problems to people.  Pigeons can also carry a number of potentially infectious diseases such as salmonella, tuberculosis and ornithosis (a mild form of psittacosis with pneumonia-like symptoms).

They are also a source of allergens, which can cause respiratory ailments like pigeon fancier's lung, aspergillosis and allergic skin reaction.  There is potential for these illnesses to be spread to people through contact with pigeon droppings, dandruff and feathers, pigeon parasites, or where dead infected pigeons get into food or water sources.  Health and safety issues and site access problems are also caused by the build up of faeces due to the slippery and unsafe footing it provides on walkways and ledges, hindering proper maintenance.  This may be a particular problem during building works and renovation.  Pigeon faeces represent a health and safety hazard for staff working in contaminated buildings and for employees and operators who have to carry out remediation works. Pigeon infestation in and around buildings therefore represent an added problem in the renovation of buildings where large accumulations have been allowed to build-up, and this nutrient rich guano combined with moisture ingress in buildings provides an ideal environment for the growth and proliferation of moulds (Singh 1994a, Singh & Walker 1996).


Histoplasmosis is caused by a fungus (Histoplasma capsulatum) and can affect both humans and animals.  Infection in humans occurs when airborne fungal spores are inhaled, especially after the nesting has been disturbed. Most infections are mild and produce either no symptoms or a minor influenza like illness. On occasion the disease can cause high fever, blood abnormalities, pneumonia and even death. The National Institutes of Health (NIH) in the USA has reported a potentially blinding eye condition, presumed ocular histoplasmosis syndrome (OHS) that probably results from the fungus.

Dusts containing H. capsulatum spores can be aerosolized during construction, excavation, or demolition.  Once airborne, spores can be carried easily by wind currents over long distances.

Histoplasmosis is an intracellular mycotic infection of the reticuloendothelial system caused by the inhalation of conidia from the fungus Histoplasma capsulatum.  Approximately 95% of cases of histoplasmosis are unobvious, subclinical or benign.  Five percent of the cases have chronic progressive lung disease, chronic cutaneous or systemic disease or an acute fulminating fatal systemic disease.  All stages of this disease may mimic tuberculosis.

Histoplasma capsulatum has a worldwide distribution; however the Mississippi-Ohio River Valley in the U.S.A. is recognized as a major endemic region. Environmental isolations of the fungus have been made from soil enriched with excreta from pigeons, chickens, starlings and bats.


Pigeon droppings appear to be the most important source of the fungus Cryptococcus neoformans in the environment.  The fungus is largely found in accumulations of droppings around roosting and nesting sites; for example, roof spaces, weather boarding, guttering, chimneystacks, windowsills, cupolas, ledges and water towers. It has been found in as many as 84 percent of samples taken from old roosts.  Dry bird droppings can be a significant source of infection.

Like histoplasmosis, cryptococcosis infections are usually mild and may be without symptoms. Persons with weakened immune systems however, are susceptible to more serious infection.  The disease is acquired by inhaling the yeast-like cells of the fungus.  Two forms of cryptococcosis occur in humans.  The generalised form begins with a lung infection and spreads to other areas of the body, particularly the central nervous system, and is usually fatal unless treated. The cutaneous (skin) form is characterised by acne-like skin eruptions or ulcers with nodules just under the skin.

In humans, C. neoformans affects immunocompromised hosts predominantly and is the commonest cause of fungal meningitis.  Meningitis is the predominant clinical presentation with fever and headache as the most common symptoms.  Secondary cutaneous infections occur and often indicate a poor prognosis. Lesions usually begin as small papules that subsequently ulcerate but may also present as abscesses, erythematous nodules, or cellulitis.


Candidiasis is a yeast or fungus infection spread by pigeons.


Psittacosis is normally mild in humans, however serious illness may occur rarely.  Pigeons and sparrows have also been implicated (along with many other species of birds) as reservoirs for encephalitis viruses.

Ticks, Mites and other Parasites

Pigeon nesting can harbour parasites including ticks and mites that may become unwanted visitors in our buildings.  Although these parasites can bite and irritate, they are unlikely to transmit diseases to humans.  Most of these parasites associated with pigeon nesting or roosting die quickly after the birds leave.

Pigeon droppings, feathers, nesting materials and dead pigeons under a roosting area can breed flies, carpet bugs, beetles and other insects that may become major problems in the immediate area.  These pests may fly through open windows or crawl through cracks to enter buildings.  These can then infest areas where people live and may cause skin irritation, disease or allergic reactions.


Feeding Pigeons

The increase in populations of feral pigeons in our cities and seaport environments has created considerable problems.  Feeding pigeons is an unhygienic and anti-social practice and encourages them to gather in increasing numbers leading to nuisance and annoyance.

Pigeons are wild birds capable of fending for themselves. Feeding feral pigeons can deprive other birds of food and might scare them from your garden.  Smaller birds such as thrushes and finches are often frightened away when numbers of much larger pigeons arrive.  Feral pigeons can also carry viruses that can be spread to other birds causing death. People who feed pigeons often end up feeding more than they bargained for.  On occasions when food is plentiful, pigeons may not always eat everything left out for them. The remaining food goes bad and may attract rats and mice, which can spread disease to humans.


Remediation Techniques & Procedures

Why to Remove Guano from Buildings?

Cleaning of pigeon guano (pigeon excrement) from the interior of a building is important for different reasons.

It is important to remove any build-up of pigeon guano in the roof voids to stop smells and reduce the potential for health hazardous and insect-related problems for occupants. Pigeon guano can have a detrimental effect on human health, where an individual who has a pre-existing respiratory condition comes into contact with large volumes of very well dried guano. In these cases it is possible that the inhalation of dust, created when large quantities of well-dried guano are disturbed, may irritate the bronchial passages.

Pigeon guano can severely compromise the aesthetics of a building and large quantities of well-dried guano in a roof space can cause smells and attract insects. Therefore it is important to remove guano, especially when it exists in large quantities within a building.


Health & Safety Procedures

It is important to carry out a health and safety risk assessment, specifically if the areas to be cleaned are at height, for example roof spaces.  Once a health and safety risk assessment has been carried out, then the areas should be cleaned and thoroughly inspected.

There are many guano cleaning chemicals and products available, including cleaning solutions and ornithological disinfectants.  When large quantities of well-dried pigeon droppings are present in roof spaces of occupied buildings or in external covered areas close to residential accommodation then bacterial-cleaning agents may be useful.

The Environment Agency allows large quantities of guano to be disposed of in a standard skip, providing that the company used is an ‘Authorised Waste Carrier’.


Pigeon Control Methods

Pigeons Proofing

Total proofing against all birds can only be guaranteed by the closure of all openings bigger than 20mm in diameter.  Pigeon proofing includes simple tasks like sealing gaps under eaves and replacing missing roof tiles.  Pigeons can be deterred from using common perching and roosting sites such as window ledges and roofs by fitting stainless steel wires suspended and sprung at the correct height to prevent the birds from landing.  Other commonly available deterrents to the feral pigeon include barrier gel, spikes and bird repellent gel.

Environmental Control

One of the most effective methods of limiting the size of flocks is by controlling feeding. Limitation of food availability will, by natural means, reduce breeding rates and discourage the influx of pigeons from other areas.


Shooting pigeons in public places is not allowed for reasons of public safety.  Shooting pigeons for example using an air gun or .22 garden gun reduces their population temporarily, however may not have significant impact on their overall population.  Gun noise from shooting can be an effective method of scaring pigeons away from a niche location.  Shooting on a regular basis in a niche location, at the time pigeons are settling for the night, may prevent a roost being established at that location.

Baiting & Poisoning

Poisoning or baiting pigeons is illegal and therefore should not be practised.  It is also difficult to ensure that other animals are not inadvertently harmed.


Trapping pigeons is ineffective and costly, because trapping techniques and operations require regular attention by an experienced operator.

It is an offence to interfere with a nest or its contents and therefore before taking any action to remove a nest, with or without eggs or chicks, permission must be sought from the Department of the Environment, Food and Rural Affairs (DEFRA).


Remediation of Guano (Pigeon Droppings)

Pigeon guano can be removed and disposed of by the maintenance operative, as long as all the necessary health and safety precautions are followed.  A specialist cleaning company would normally be called in for the clearance of guano in large-scale roosts that have been used for many years when there are large quantities of well-dried guano present.

Dealing with guano accumulations in building roof voids can be expensive and time consuming because of the protective equipment and procedures that may be required.  It is recommended to employ a company fully trained in the removal, cleaning and sanitisation of areas that have been affected by pigeon droppings, to ensure the procedure is performed in an efficient and safe manner.

Operators should follow certain precautions to minimize risk from disease organisms in the droppings:

  • During the remediation works, only authorised clean-up personnel should be present.
  • Healthy individuals should carry out the remediation.
  • It is recommended to use a respirator that can filter particles as small as 0.3 microns.
  • It is recommended to use disposable protective gloves, hat, overalls and shoe coverings.
  • It is recommended to moisten the droppings with a light mist of water to keep spores from becoming airborne and keep them wet.
  • It is recommended to bag the droppings into sealed plastic bags.  The outside of the bags should be rinsed off before they are placed in a disposal container.
  • When finished the remediation works and while still wearing the respirator, remove protective clothing and place it in a plastic bag.
  • Upon completion of the remediation works, it is recommended to have a   shower.
  • Dispose of waste through a safe manner in accordance with local authority regulations.
  • Guano removal from site should comply with Waste Disposal Regulations 1994.
  • It is recommended to employ bird-proofing measures to deter pigeons on the building fabric and components.



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P Ehrlich et al, The Birder’s Handbook: A Field Guide to the Natural History of Northern American Birds, Simon & Schuster, New York and London, 1988

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Pathology and Control. Review in Indoor Built Environ 1999; 8:3-20.

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